Presented as a girl introduced by his younger brother, the seemingly pure girlfriend is actually an extremely promiscuous girl who enjoys seducing people close to her. When she provocatively invites the older brother to have sex, he lies and says, "I'm only interested in anal." Believing his words, she later visits his room specifically seeking anal sex. Unable to resist her exposed anus, the older brother ends up indulging in three straight days of intense anal intercourse with her. The story captivates with its unique progression and the intense tension between the girl and the brother, focusing heavily on a deeply intimate relationship centered around anal sex.